Flow analysis and design of dialyzers

Generally, dialyzers support or replace the kidney function. The central part of the dialyzer is a hollow fibre bundle of semi-permeable membranes, which accomplishes the removal of toxic agents from the blood.

Object of the numerical simulation is on one hand the analysis of the global and local flow conditions as well as the mass transfer in the dialyzer. On the other hand, this is utilised to characterise and optimise its clearance properties.

Method - "The virtual dialyser" consists of a 3D model of the complete dialyzer to determine the velocity and pressure distribution in both, the dialysate and the blood compartments. A local model of the hollow fibres computes the diffusive and convective mass transfer along and through the membrane.

Results of the simulations show how the clearance rate is influenced by the membrane properties (permeability), by the fibre geometry and by the flow conditions around the hollow fibre. The model enables detailed predictions of the clearance rate for all relevant species (urea, creatinine, vitamine B12,…). The virtual dialyzer is used to optimise dialyzers efficiently by parameter and geometry variations and to predict the dialyzer function and its hemocompatibility (haemolysis, thrombosis) already before prototypes are built.